ES2379900T3 - Lithium battery and method to manufacture an anode from it - Google Patents

Abstract

A lithium battery includes an anode and a cathode. The anode includes a first carbon nanotube structure, the first carbon nanotube structure incudes at least a carbon nanotube film. The cathode includes a second carbon nanotube structure, the second carbon nanotube structure including a carbon nanotube film structure and a plurality of active material particles dispersed in the carbon nanotube film structure. A method for making the anode of a lithium battery includes the steps of: providing an array of carbon nanotubes; making a first carbon nanotube structure; providing a negative current collector; and disposing the first carbon nanotube structure on the current collector, and thereby, achieving the anode of lithium battery.

Description

Lithium battery and method to manufacture an anode from it

Field of the Invention

The present invention relates to a lithium battery, and to a method of manufacturing a lithium battery anode.

Discussion of related technique

In recent years, lithium batteries have received a lot of attention and are used in various portable devices, such as portable personal computers, mobile phones and digital cameras, due to their low weight, high discharge voltage, long cycle life and high energy density compared to conventional lead-acid storage batteries, nickel-cadmium batteries, nickel-hydride batteries, and nickel-zinc batteries.

A lithium battery generally includes a cathode, an anode, electrolyte, a separator used to separate the anode from the cathode, and a container having the anode, cathode, electrolyte, and separator disposed therein.

An anode of a lithium battery must have properties such as high energy density; a low open circuit voltage against metallic lithium electrodes; high capacity retention; good performance in common electrolytes; high density (for example,> 2.0 g / cm3); Good stability during loading and unloading processes, and low cost. At present, the most widely used active material for the anode is carbonaceous / carbonaceous material such as natural graphite, artificial graphite and amorphous carbon. Amorphous carbon has an excellent capacity, but its irreversibility is relatively high. The maximum theoretical capacity of natural graphite is 372 mAh / g, but its life is relatively short.

In general, the anode of carbonaceous / carbonaceous material has low efficiency and low cycling performance in the first charge and discharge cycle, due to the formation of an electrolyte-solid interface (SEI) layer. A stable SEI layer is essential in the lithium battery to prevent the anode material from reacting with the electrolyte, therefore, the selection of the electrolyte is limited. Only electrolytes in which a stable SEI layer can be formed are suitable for use in a lithium battery.

Carbon nanotubes are a new carbonaceous / carbonaceous material formed by one or more layers of graphite. The distance between two layers of graphite in the carbon nanotube is approximately 0.34 nanometers, which is greater than the distance between two layers of natural graphite. Thus, the carbon nanotube is a material suitable for use as a lithium battery anode. However, until now, carbon nanotubes are mixed with a binder, and are arranged on a current collector of the anode. As such, the adsorption capacity of carbon nanotubes is restricted by the binder mixed with them.

A cathode of a lithium battery must have properties such as high energy density; high voltage open circuit in front of the metallic lithium electrode; high capacity retention; good performance in common electrolytes; high density; Good stability during loading and unloading processes, and low cost. Among various active materials, transition metal oxides and mixed transition metal oxides have received much attention, due to their relatively high charge / discharge capabilities in lithium batteries. At present, the most widely used cathode active materials are spinel-type lithium and manganese oxide (for example, LiMn2O4), olivine-type lithium iron and phosphate (for example, LiFePO4), and lithium oxide and stratified cobalt (for example, LiCoO2).

However, the low conductivity of the active materials generally induces a relatively large resistance in the cathode. As such, the charge / discharge depth of the lithium battery is relatively low. To decrease the resistance of the cathode, a conductive additive is commonly mixed with the active material. The weight of the conductive additive can reach approximately 15% ~ 30% of the total cathode weight. If the conductive additive increases and the weight of the battery must remain the same, the amount of active material in the cathode must be reduced, and thus, the energy density of the lithium battery will be affected.

To solve the problem described above, carbon nanotubes have been tested as a new conductive additive, in lithium battery cathodes, to take advantage of their excellent conductive properties. In the prior art, powdered carbon nanotubes are mixed with the active material by ultrasonic stirring. Unfortunately, carbon nanotubes are prone to aggregation due to their extremely large specific surface area, and as such, aggregate carbon nanotubes will not improve the conductivity of the cathode.

What is needed, therefore, is to provide a lithium battery with an anode with a good adsorption capacity, a lithium battery with a cathode that has good conductivity, and a method for manufacturing the lithium battery anode, and, in which, the above problems are eliminated or at least mitigated.

Summary

Thus, seen from one aspect, the present invention provides a lithium battery, comprising:

an anode comprising a carbon nanotube film structure comprising at least two overlapping carbon nanotube films, in which each carbon nanotube film comprises a plurality of consecutive carbon nanotubes joined end to end, and aligned to the along one

same direction;

 a cathode;

a separator used to separate the anode from the cathode;

a vessel with the anode, cathode and separator disposed therein; Y

an electrolyte that fills the container. Viewed from a further aspect, the present invention provides a lithium battery, comprising: an anode; a cathode comprising a carbon nanotube film structure comprising at least two overlapping carbon nanotube films, and a plurality of particles of active material dispersed in the carbon nanotube film structure, in which each nanotube film Carbon comprises a plurality of consecutive carbon nanotubes joined end to end, and aligned along the same direction; a separator used to separate the anode from the cathode; a vessel with the anode, cathode and separator disposed therein; and an electrolyte that fills the container. Seen from yet another additional aspect, the present invention provides a method for manufacturing an anode of a

lithium battery, the method comprising the steps of:

(to)

provide a disposition of carbon nanotubes;

(b)

preparing a carbon nanotube film structure comprising at least two overlapping carbon nanotube films, wherein each carbon nanotube film comprises a plurality of consecutive carbon nanotubes joined end to end and aligned along the same address;

(C)

provide a negative current collector; Y

(d)

arrange a carbon nanotube film structure on the current collector, and thereby obtain the lithium battery anode.

Other advantages and new features of the lithium battery of the present invention, and the related method of manufacturing the anode, will be more apparent from the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings.

Brief description of the drawings

Many aspects of the lithium battery of the present invention, and the related method of manufacturing the lithium battery anode, will be better understood with reference to the following drawings. The components in the drawings do not necessarily have to be scaled, emphasizing instead a clear illustration of the principles of the lithium battery of the present invention and the related method of manufacturing the lithium battery anode, and a battery of lithium using it.

Figure 1 is a schematic view of an anode of a lithium battery, in accordance with an embodiment of the present invention.

Figure 2 shows a scanning electron microscopy (SEM) image of a film of carbon nanotubes at the anode of the lithium battery according to an embodiment of the present invention.

Figure 3 shows a scanning electron microscopy (SEM) image of a carbon nanotube film arranged in the anode according to an embodiment of the present invention.

Figure 4 shows a photograph of a film of carbon nanotubes with a predetermined shape at the anode of the lithium battery of Figure 1.

Figure 5 shows a scanning electron microscopy (SEM) image of a carbon nanotube film structure, in accordance with the present embodiment.

Figure 6 shows a schematic view of a composite film, according to the carbon nanotube structure of the anode of a lithium battery.

Fig. 7 is a flow chart of a method for manufacturing the anode of the lithium battery according to an embodiment of the present invention.

Figure 8 shows a photograph of a carbon nanotube floc structure at the anode of the lithium battery of Figure 1.

Figure 9 is a schematic view of a cathode of a lithium battery, in accordance with an embodiment of the present invention.

Figure 10 is a schematic view of a second carbon nanotube structure used in the cathode of the lithium battery of Figure 9.

Figure 11 is a flow chart of a method for manufacturing the lithium battery cathode according to an embodiment of the present invention.

Fig. 12 is a schematic view of a lithium battery, in accordance with the present embodiment.

The corresponding reference characters indicate the corresponding parts throughout the various views. The examples shown here illustrate at least one preferred embodiment of the lithium battery of the present invention and the related method of manufacturing the anode thereof, in at least one form, and such examples are not to be construed as limiting the scope of The invention in any way.

Detailed description of the preferred embodiments

Reference will now be made to the drawings, to describe in detail embodiments of the lithium battery of the present invention, and a related method for manufacturing the anode thereof.

Referring to Fig. 1, an anode 10 of a lithium battery in the present embodiment includes a negative current collector 12 and a first carbon nanotube structure 14 held by the negative current collector 12. The first nanotube structure Carbon 14 includes at least one film of carbon nanotubes. The negative current collector 12 may be beneficially a metallic substrate. Very suitably, the metal substrate is a copper foil. The first carbon nanotube structure 14 can be advantageously arranged directly on a surface of the negative current collector

12. More specifically, the first carbon nanotube structure 14 can be formed on the surface of the negative current collector 12 directly, or it can be prepared to adhere to the surface of the negative current collector 12 by means of a binder.

Referring to Figure 2 and Figure 3, the first carbon nanotube structure 14 may be an independent carbon nanotube film. In addition, carbon nanotubes are substantially parallel to a surface of the first carbon nanotube structure 14. Carbon nanotubes are selected from the group consisting of isotropically arranged carbon nanotubes, arranged along a certain direction. , or arranged along different directions. Adjacent carbon nanotubes are combined and attracted by the attractive force of Van der Waals, thus forming an independent structure. As such, the first carbon nanotube structure 14 has good tensile strength, and may, advantageously, be shaped in most of the desired anode shapes. The first carbon nanotube structure 14 includes a plurality of micropores. The diameter of the micropores is less than 1 micrometer. As such, the specific surface area of the first carbon nanotube structure 14 is extremely large. Thus, when the first carbon nanotube structure 14 is used in the anode of the lithium battery, the amount of intercalation of lithium ions can be increased, and the stability of an SEI layer formed in the first cycle of loading / unloading, due to the special microporous structure of the first carbon nanotube structure 14.

Referring to Figure 4, the first carbon nanotube structure 14 may be a film of carbon nanotubes with a plurality of isotropic and uniformly arranged, disordered, and entangled carbon nanotubes. The first carbon nanotube structure 14 includes a plurality of micropores formed by the disordered carbon nanotubes. The diameter of the micropores is less than 100 micrometers. As such, the specific surface area of the first carbon nanotube structure 14 is extremely large. Thus, when the first carbon nanotube structure 14 is used at the anode of the lithium battery, the amount of intercalation of the lithium ions can be increased, and the stability of the SEI layer formed in the first cycle can be improved. loading / unloading, due to the special microporous structure of the first carbon nanotube structure 14.

Referring to Figure 5, the first carbon nanotube structure 14 includes at least one carbon nanotube film. The carbon nanotube film includes a plurality of consecutive carbon nanotubes joined end to end and aligned along the same direction. When the first carbon nanotube structure includes a plurality of carbon nanotube films, the layers of the carbon nanotube film intersect and overlap with each other. The angle between the aligned directions of two adjacent layers is arbitrary.

Referring to Figure 6, the first carbon nanotube structure 14 may be a composite film. The composite film includes a structure of carbon nanotube films 16 and a plurality of nanoscale tin oxide particles 18 dispersed in the structure of carbon nanotube films 16. The structure of carbon nanotube films 16 includes the minus two overlapping carbon nanotube films. The carbon nanotube film includes a plurality of consecutive carbon nanotubes joined end to end and aligned along the same direction. The at least two carbon nanotube films intersect and overlap with each other. The number of carbon nanotube films and the angle between the aligned directions of the two adjacent carbon nanotube films is arbitrarily set.

The carbon nanotube film in the carbon nanotube film structure 16 may also include a plurality of carbon nanotubes. Carbon nanotubes are isotropic and are uniformly arranged, messy, and entangled together.

The carbon nanotube film in the carbon nanotube film structure 16 may also include a plurality of carbon nanotubes. Carbon nanotubes are arranged isotropically, arranged along a certain direction, or arranged along different directions.

It is to be understood that the negative current collector 12, at the anode 10 of the lithium battery of the present embodiment, is optional. In other embodiments, the anode 10 of the lithium battery may include only the first carbon nanotube structure 14. Due to the independent and stable film structure, the first carbon nanotube structure 14 can be used as the anode 10 of the battery lithium, without the negative current collector 12.

In the present embodiment, the width of the carbon nanotube structure 14 is in the approximate range of 1 cm to 10 cm. The thickness of the first carbon nanotube structure 14 is in the approximate range of 1 micrometer to 2 mm. It is to be understood that the size of the carbon nanotube structure 14 can be set arbitrarily. After a cutting step, a film of carbon nanotubes of a smaller size (for example, 8 mm x 8 mm) can be formed, for use as an anode with a carbon nanotube base in a miniature lithium battery.

Referring to Figure 7, a method of manufacturing the anode 10 of the lithium battery includes the steps of: (a) providing a carbon nanotube arrangement, very suitably, providing a super-aligned arrangement of carbon nanotubes; (b) prepare a first carbon nanotube structure 14; (c) provide a negative current collector 12; and (d) arranging the first carbon nanotube structure 14 on the negative current collector 12 to obtain the anode 10 of the lithium battery.

In step (a), a given super-aligned arrangement of carbon nanotubes can be formed, by the steps of: (a1) providing a substantially flat and smooth substrate; (a2) form a catalyst layer on the substrate; (a3) annealing the substrate with the catalyst at a temperature in the approximate range of 700 ° C to 900 ° C in air for 30 to 90 minutes; (a4) heating the substrate with the catalyst at a temperature in the approximate range of 500 ° C to 740 ° C in an oven with a protective gas inside it; and (a5) supply a gas as a carbon source to the oven for 5 to 30 minutes, and grow a super-aligned arrangement of carbon nanotubes from the substrate.

In step (a1), the substrate can be a P or N type silicon wafer. Very suitably, a 100 mm (4 inch) P type silicon wafer is used as the substrate.

In step (a2), the catalyst can be prepared from iron (Fe), cobalt (Co), nickel (Ni), or any of its alloy combinations.

In step (a4), the protective gas can be prepared from at least one of nitrogen (N2), ammonia (NH3), and a noble gas. In step (a5), the gas as a carbon source may be a hydrocarbon gas, such as ethylene (C2H4), methane (CH4), acetylene (C2H2), ethane (C2H6), or any combination thereof.

The super-aligned arrangement of carbon nanotubes may have a height greater than 100 micrometers, and includes a plurality of carbon nanotubes parallel to each other, and approximately perpendicular to the substrate. The super-aligned arrangement of carbon nanotubes formed in the above conditions has substantially no impurities, such as carbonaceous or residual particles of the catalyst. The carbon nanotubes in the super-aligned arrangement are packed together closely by the attractive force of Van der Waals.

In step (b), the first carbon nanotube structure 14 can be formed by the steps of: (b1) providing a pressure device, and (b2) pressing on the arrangement of carbon nanotubes to form a nanotube film carbon, and obtain a first carbon nanotube structure 14.

A certain pressure can be beneficially applied to the arrangement of carbon nanotubes by means of the pressure device. In the pressure process, the carbon nanotubes of the carbon nanotube arrangement are separated from the substrate, and form under pressure the film of carbon nanotubes. Carbon nanotubes are substantially parallel to a surface of the carbon nanotube film.

In the present embodiment, the pressure device can advantageously be a pressure head. The pressure head has a smooth surface. It is to be understood that the shape of the pressure head and the direction of the pressure can, in a timely manner, determine the direction of the carbon nanotubes disposed there. Referring to Figure 2, when a flat pressure head is used to press on the arrangement of carbon nanotubes along the direction perpendicular to the substrate, a film of carbon nanotubes with a plurality of can be advantageously obtained Carbon nanotubes arranged in an isotropic manner. Referring to Figure 3, when a roller-shaped pressure head is used to pressure the arrangement of carbon nanotubes along a certain direction, a film of carbon nanotubes with a plurality of carbon nanotubes is obtained. aligned along that certain direction. When a roller-shaped head is used to pressure the arrangement of carbon nanotubes along different directions, a film of carbon nanotubes with a plurality of carbon nanotubes aligned along different directions is obtained.

In step (b), the first carbon nanotube structure 14 can be formed by the steps of: (b1 ') separating the arrangement of carbon nanotubes from the substrate to obtain a plurality of carbon nanotubes; (b2 ’) add the plurality of carbon nanotubes to a solvent to obtain a carbon nanotube floc structure in the solvent; and (b3 ') separating the carbon nanotube floc structure from the solvent, and forming the carbon nanotube floc structure as a carbon nanotube film, and thereby obtaining the first carbon nanotube structure 14.

In step (b1 '), the arrangement of carbon nanotubes 14 can be removed by scraping the substrate with a knife or other similar device, to obtain a plurality of carbon nanotubes. Such starting material is capable, to some extent, of maintaining the segmented state of carbon nanotubes. The length of carbon nanotubes is above 10 micrometers.

In step (b2 ’), the solvent is selected from a group consisting of water and a volatile organic solvent. After adding the plurality of carbon nanotubes to the solvent, a process for flocculating the carbon nanotubes can be suitably executed to create the carbon nanotube floc structure. The process of flocculating carbon nanotubes can be beneficially selected from the group consisting of ultrasonic dispersion of carbon nanotubes and agitation of carbon nanotubes. In this embodiment, the ultrasonic dispersion is used to flocculate the solvent containing the carbon nanotubes for approximately 10 ~ 30 minutes. Because the carbon nanotubes in the solvent have a large specific surface since the entangled carbon nanotubes have an attractive force of large Van der Waals, the flocculated and entangled carbon nanotubes form a network structure (i.e., structure of flocs).

In step (b3 ’), the process of separating the floc structure from the solvent includes the sub-stages of: (b3’1) filtering off the solvent to obtain the carbon nanotube floc structure; and (b3’2) drying the carbon nanotube floc structure to obtain the separated carbon nanotube floc structure.

In step (b3’2), the carbon nanotube floc structure can be set at room temperature for a period of time to dry the organic solvent. Drying time can be selected according to practical needs. Referring to Figure 8, on the filter, the carbon nanotubes in the carbon nanotube floc structure are entangled together.

In step (b3 '), the method of shaping includes the sub-stages of: (b3'3) placing the separated carbon nanotube floc structure in a container (not shown), and extending the nanotube floc structure of carbon to form a predetermined structure; (b3’4) press on the extended carbon nanotube floc structure with a certain pressure to give rise to a desired shape; and (b3’5) remove the residual solvent contained in the extended floc structure to form the carbon nanotube film.

It is to be understood that the size of the extended floc structure has to be used, advantageously, to control the thickness and surface density of the first carbon nanotube structure 14. As such, the larger the surface of the structure of floccules, the thickness and density of the first carbon nanotube structure 14 will be smaller. Referring to Figure 3, in the embodiment, the thickness of the first carbon nanotube structure 14 is in the approximate range of 1 micrometer to 2 millimeters, and the width of the first carbon nanotube structure 14 may be, in a timely manner, in the approximate range of 1 cm to 10 cm.

In addition, step (b3 ') can be carried out by a pumping and filtration process of the carbon nanotube floc structure, to obtain the carbon nanotube film. The filtration and pumping process includes the sub-stages of: (b3’1 ’) providing a microporous membrane and an air funnel; (b3’2 ’) filter off the solvent from flocculated carbon nanotubes through the microporous membrane, using the funnel for pumping air; and (b3’3 ’) pump with air and dry the flocculated carbon nanotubes stuck on the microporous membrane.

In stage (b3’1 ’), the microporous membrane has a smooth surface. And the diameter of the micropores of the membrane is approximately 0.22 micrometers. The pumping filtration can exert air pressure on the floc structure, thus forming a first uniform carbon nanotube structure 14. Furthermore, because the microporous membrane has a smooth surface, the carbon nanotube film can separate easily.

Through the flocculation stage, carbon nanotubes become entangled with each other due to the attractive force of Van der Waals, to form a network structure / floc structure. Thus, the first carbon nanotube structure 14 has a good tensile strength. The first carbon nanotube structure 14 includes a plurality of micropores formed by the disordered carbon nanotubes. The diameter of the micropores is less than 100 micrometers. As such, the specific surface area of the first carbon nanotube structure 14 is extremely large. Additionally, the carbon nanotube film has essentially no binder, and includes a large amount of micropores. Therefore, when the first carbon nanotube structure 14 is used at the anode of the lithium battery, the amount of intercalation of the lithium ions can be increased, and the stability of the SEI layer formed in the first cycle of loading / unloading, due to the special microporous structure of the first carbon nanotube structure 14. In addition, the method for manufacturing the first carbon nanotube structure 14 is simple, and can be used for series production. A result of the method production process is that the thickness and surface density of the first carbon nanotube structure 14 are controllable.

It will be apparent to persons of normal skill in the field of the present invention, that the size of the first carbon nanotube structure 14 can be arbitrarily set, and depends on the actual needs of use (for example, a miniature lithium battery ). The first carbon nanotube structure 14 can be cut into smaller sizes outdoors.

In step (b), the first carbon nanotube structure 14 can be formed by the steps of: (b1 ”) extracting at least two carbon nanotube films from the carbon nanotube arrangement, using a utensil (for example, masking tape or other utensil that allows multiple carbon nanotubes to adhere and remove simultaneously); and (b2 ”) provide a support member and arrange the carbon nanotube films in the support member along different directions, the carbon nanotube films overlapping each other to obtain the first carbon nanotube structure 14 .

In step (b1 ”), the carbon nanotube films can be beneficially extracted from the super-aligned arrangement of carbon nanotubes, by means of the sub-stages of: (b1” 1) selecting a plurality of carbon nanotube segments with a predetermined width; (b1 "2) remove the carbon nanotube segments at a constant / uniform rate to form a film of carbon nanotubes; (b1 "3) repeat step (b1" 1) and (b1 "2) to form a plurality of carbon nanotube films.

In step (b1 "1), very usefully, the segments of carbon nanotubes with a predetermined width can be selected using a wide adhesive tape as a tool to make contact with the super-aligned arrangement. In step (b1 "2), the extraction direction is, in a useful manner, substantially perpendicular to the direction of growth of the super-aligned arrangement of carbon nanotubes.

More specifically, during the extraction procedure, while the initial carbon nanotube segments are removed, other end-to-end nanotube segments are also removed, due to the attractive force of Van der Waals between ends of adjacent segments. This extraction procedure ensures that a film of consecutive carbon nanotubes can be formed. The carbon nanotubes of the carbon nanotube film are all substantially parallel to the direction of removal, and the carbon nanotube film produced in such a manner is capable of being formed to have a predetermined selectable width.

The width of the first carbon nanotube film depends on the size of the carbon nanotube arrangement. The length of the first carbon nanotube film is arbitrary. In a useful embodiment, when the substrate size is 10.16 cm (4 inches), the width of the first carbon nanotube film is in the approximate range from 1 cm to 10 cm, and the thickness of the first film of carbon nanotubes is in the approximate range from 0.01 to 100 micrometers.

In step (b), the first carbon nanotube structure 14 can be formed by the steps of: (b1 ’’) preparing at least two carbon nanotube films; (b2 ’’ ’) overlap at least two carbon nanotube films to achieve a carbon nanotube film structure 16; (b3 ’’ ’) dispersing a plurality of nanoscale tin oxide particles 18 in the carbon nanotube film structure 16 to form a composite film, then obtaining a first carbon nanotube structure 14.

In stage (b1 ’’), the carbon nanotube film can be prepared by a flocculation method, a pressure method, or an extraction method.

The flocculation method for obtaining a carbon nanotube film includes the following steps: separating the arrangement of carbon nanotubes from the substrate to obtain a plurality of carbon nanotubes; adding a plurality of carbon nanotubes to a solvent to create a carbon nanotube floc structure in the solvent; separate the carbon nanotube floc structure from the solvent; and to form the carbon nanotube floc structure of carbon nanotubes. The carbon nanotube film prepared by the flocculation method includes a plurality of isotropic carbon nanotubes entangled with each other and distributed in a disorderly manner.

The pressure method for obtaining a film of carbon nanotubes includes the following steps: pressure on the arrangement of carbon nanotubes using a compression apparatus, thereby forming a film of carbon nanotubes. The carbon nanotube film prepared by the pressure method includes a plurality of carbon nanotubes aligned along one or more directions.

In the present embodiment, the extraction method is adopted to prepare the carbon nanotube film.

In step (b2 '' '), after being removed from the carbon nanotube arrangement, the carbon nanotube films can be usefully overlapped with each other to form a structure of carbon nanotube films 16. It should be noted that because the carbon nanotubes in the super-aligned arrangement of step (a) have a high purity and a high specific surface area, the carbon nanotube film is adhesive. As such, adjacent carbon nanotube films are combined by the attractive force of Van der Waals to form a stable structure of carbon nanotube films 16. The number of carbon nanotube films and the angle between the aligned directions of two Adjacent carbon nanotube films can be arbitrarily fixed or fixed according to actual needs / use. Very usefully, in the present embodiment, the carbon nanotube film structure 16 includes 200 carbon nanotube films, and the angle between the aligned directions of two adjacent carbon nanotube films can be, in a timely manner, approximately 90 ° .

Very suitably, an additional stage (b4 '' ') of treating the carbon nanotube film structure 16 at the anode 10 of the battery of battery can be provided advantageously, after step (b2' ''). Lithium with an organic solvent.

In step (b4 ''), the carbon nanotube film structure 16 can be beneficially treated by either of two methods: dropping an organic solvent from an eyedropper to soak a full surface of the film structure of carbon nanotubes 16, or immerse the carbon nanotube film structure 16 in a container containing an organic solvent. The organic solvent may be volatilized, and may be selected from the group consisting of ethanol, methanol, acetone, dichloroethane, chloroform, and combinations thereof. Very suitably, the organic solvent is ethanol. After soaking with the organic solvent, the carbon nanotube segments of the carbon nanotube film structure 16 can at least partially shrink to form carbon nanotube fibers due to the surface tension created by the organic solvent. Due to the decrease of the specific surface by means of packaging, the friction coefficient of the carbon nanotube film structure 16 is reduced, but the structure of carbon nanotube films 16 maintains a high mechanical strength and hardness. As such, the carbon nanotube film structure 16 can be used usefully after the treatment procedure. Furthermore, after being treated with the organic solvent, due to the shrinking of the carbon nanotube segments to form carbon nanotube fibers, the parallel carbon nanotube segments in a layer are relatively far apart (especially compared to the initial distribution of the carbon nanotube segments) from each other, and are oriented transversely to the parallel carbon nanotube segments of adjacent layers. As such, the structure of carbon nanotube films 16 with a microporous structure can be formed in this way (ie, micropores are defined by the gaps / gaps between adjacent segments).

It is to be understood that the microporous structure is related to the number of layers of the carbon nanotube film structure 16. The greater the number of layers formed in the structure of carbon nanotube films 16, the greater the number of segments in the carbon nanotube film structure 16. Consequently, the space between adjacent segments and the diameter of the micropores will be reduced.

It will be apparent to persons of normal skill in the field of the present invention, that the size of the carbon nanotube film structure 16 is arbitrary, and depends on the actual needs of use (for example, a miniature lithium battery ). A laser beam can be used to cut the structure of carbon nanotube films 16 into smaller sizes outdoors.

In step (b3 ’’), the first carbon nanotube structure 14 can be advantageously formed by the sub-stages of: (b3 ’’ 1) modifying the structure of carbon nanotube films 16; (b3 ’’ 2) coating the modified carbon nanotube film structure 16 with a polymer; (b3 ’’ ’3) cover the structure of 16 carbon nanotube films with tin salt; (b3 ’’ ’4) hydrolyze the tin ion of the tin salt to form the nanoscale tin oxide particles 18; and (b3 ’’ 5) heat the carbon nanotube film structure 16 to remove the polymer, then obtaining a first carbon nanotube structure 14.

In step (b3 ’’ 1), the carbon nanotube film structure 16 is arranged in a container containing an inorganic acid, at a temperature of 90 ° C to 140 ° C for 4 to 6 hours. The ends of the carbon nanotubes are open by acid corrosion. In addition, the inner wall and the outer wall of the carbon nanotubes are modified (ie, modification of the surface of the carbon nanotubes). In the present embodiment, the carbon nanotube film structure 16 is arranged in a very high pressure boiler with nitric acid inside, at about 120 ° C for about 5 hours.

In step (b3 ’’ 2), the modified carbon nanotube film structure 16 is immersed in a polymer solution for 5 to 7 hours. After coating with the polymer, the carbon nanotube film structure 16 is washed to remove the unstable and excess polymer. Very suitably, the carbon nanotube film structure 16 is immersed in a solution of polyvinylpyrrolidone (PVP) in ethanol or acetone as solvent.

In step (b3 ’’ 3), the polymer-coated carbon nanotube film structure 16 is arranged in a container with a solution of tin ions, at a temperature of 90 ° C to 110 ° C, for 2 to 4 hours. Then, the container is cooled freely to room temperature. As such, a tin salt is formed on the surface of the polymer-coated carbon nanotube film structure 16. The solution of tin ions can be beneficially a solution of an inorganic tin salt in water or an organic tin compound in ethanol or acetone. The concentration of tin ion in the solution can be, in a timely manner, in the approximate range of 3 mol / l to 10 mol / l. In the present embodiment, the polymer-coated carbon nanotube film structure 16 is arranged in a very high pressure boiler with a solution of tin dichloride dihydrate (SnCl2.2H2O) at about 100 ° C for about 3 hours. After cooling freely to room temperature, the unstable and excess tin salt on the carbon nanotube film structure 16 is removed using acetone.

In stage (b3 ’’ 4), the carbon nanotube film structure 16 is submerged in water. The tin ion in the tin salt can be hydrolyzed to form the nanoscale tin oxide particles 18 at room temperature. In addition, tin ion can be rapidly hydrolyzed at high temperature or in alkaline conditions. In the present embodiment, very suitably, the carbon nanotube film structure 16 is immersed in ammonia at 50 ° C. As such, the nanoscale tin oxide particles 18 are formed and adsorbed on the walls of the carbon nanotubes of the carbon nanotube film structure 16, or fill the gaps / gaps of the nanotube film structure of carbon 16.

In stage (b3 ’’ 5), the polymer that covers the structure of carbon nanotube films 16 decomposes at high temperature. Very usefully, the carbon nanotube film structure 16 coated with the polymer can be heated at a temperature of 300 ° C to 400 ° C for 20 to 40 minutes in a protective gas (for example, nitrogen (N2), or a noble gas). In the present embodiment, the polymer-coated carbon nanotube film structure 16 is heated at 350 ° C for approximately 30 minutes, to obtain the first carbon nanotube structure 14.

In step (d), the first carbon nanotube structure 14 can be prepared, suitably, to adhere to the surface of the negative current collector 12 by means of a binder.

It is to be understood that, when the first carbon nanotube structure 14 includes only a plurality of carbon nanotubes, the first carbon nanotube structure 14 is adhesive due to its large specific surface area, thus, the first nanotube structure of Carbon 14 can adhere directly to the negative current collector 12 by the attractive force of Van der Waals.

In step (c), the negative current collector 12 may be beneficially a metal substrate. Very suitably, the metal substrate is a copper foil.

It is to be understood that, the negative current collector 12 at the anode 10 of the lithium battery of the present embodiment is optional. In other embodiments, the anode 10 of the lithium battery may include only the first carbon nanotube structure 14. Due to the independent and stable structure of the film, the first carbon nanotube structure 14 can be used as the anode 10 of the lithium battery, without the negative current collector 12.

Referring to Figure 9 and Figure 10, a cathode 20 of the present embodiment includes a positive current collector 22 and a second carbon nanotube structure 24 disposed on the positive current collector 22. The positive current collector 22 may be, beneficially, a metallic substrate. Very suitably, the metal substrate is a copper foil. The second carbon nanotube structure 24 includes a structure of carbon nanotube films 16, and a plurality of particles of active material 28 dispersed in the structure of carbon nanotube films 16.

The carbon nanotube film structure 16 includes at least two overlapping carbon nanotube films. Each carbon nanotube film includes a plurality of consecutive carbon nanotube segments joined end to end and aligned in the same direction. The at least two carbon nanotube films intersect and overlap with each other. The number of carbon nanotube films and the angle between the aligned directions of the two adjacent carbon nanotube films is arbitrarily set.

In the present embodiment, the width of the carbon nanotube film structure 16 may suitably be in the approximate range of 1 cm to 10 cm, and the thickness of the carbon nanotube film structure 16 may be, of useful way, in the approximate range of 0.01 micrometers to 100 micrometers. The structure of carbon nanotube films 16 with a plurality of micropores defined by the space between adjacent carbon nanotube segments. The diameter of the resulting micropores may be beneficially less than 100 nanometers.

Referring to Figure 5, very suitably, the structure of carbon nanotube films 16 includes 200 films of carbon nanotubes overlapping each other. In the present embodiment, the width of the carbon nanotube film structure 16 is approximately 5 cm, and the thickness of the carbon nanotube film structure 16 is approximately 50 micrometers. The angle between the aligned directions of two adjacent carbon nanotube films is approximately 90 °. The diameter of each of the micropores is approximately 60 nanometers.

The particles of active material 28 are adsorbed on the wall of the carbon nanotubes by the attractive force of Van der Waals, or fill the space between adjacent carbon nanotube segments of the carbon nanotube film structure 16. The size of the particles of active material 28 may be, in a timely manner, nanoscale. Very suitably, the diameter of the active material particles 28 is in the approximate range from 3 nanometers to 10 nanometers. In the present embodiment, the diameter of the particles of active material 28 is approximately 6 nanometers.

The active material particles 28 can be prepared, in a timely manner, from transition metal oxides and mixed transition metal oxides such as lithium oxide and spinel manganese oxide (eg, LiMn2O4), lithium iron phosphate type olivine (for example, LiFePO4), and stratified lithium and cobalt oxide (for example, LiCoO2).

It is to be understood that the positive current collector 22, at the cathode 20 of the lithium battery of the present embodiment, is optional. In another embodiment, the cathode 20 of the lithium battery may include only the second carbon nanotube structure 24. Due to the plurality of carbon nanotube films that are stacked to form a self-sustaining and stable film structure, the structure of Carbon nanotube films 16 can be used as a cathode 20 in the lithium battery without the positive current collector 22.

The carbon nanotube film structure 16 in the present embodiment has an extremely large specific surface area (ie, surface area per gram of solid material). As such, a relatively large amount of particles of active material 28 can be adsorbed on the walls of the carbon nanotubes or fill the micropores of the carbon nanotube structure 14. Accordingly, the charge / discharge capacity of the battery can be improved of lithium using the cathode based on carbon nanotubes described above. In addition, since the particles of active material are uniformly dispersed in the second carbon nanotube structure 24, the conductivity of the cathode can be increased.

Referring to Figure 11, a method of manufacturing the cathode 20 of the lithium battery includes the steps of:

(e) provide at least two carbon nanotube films to form a carbon nanotube film structure 16; and (f) providing a plurality of active material particles 18, dispersing the active material particles 28 in the carbon nanotube structure 16 to form a second carbon nanotube structure 24; (g) provide a positive current collector 22, and arrange the second carbon nanotube structure 24 on the positive current collector 22 to obtain the cathode 20 of the lithium battery.

In step (f), the second carbon nanotube structure 14 can be advantageously formed by the sub-stages of: (f1) providing a preform or a precursor of the active material; (f2) immersing the carbon nanotube film structure 16 in the preform or precursor of the active material to form the second carbon nanotube structure 24.

The active material may be, in a timely manner, transition metal oxides and mixed transition metal oxides such as spinel-type lithium oxide and manganese (for example, LiMn2O4), olivine-type lithium iron and phosphate (for example , LiFePO4), and stratified lithium and cobalt oxide (for example, LiCoO2).

In a useful embodiment of step (f), the preform of the active material may suitably be a mixture of the active material and a solvent. The solvent can be beneficially selected from the group consisting of water, ethanol, acetone, and combinations thereof. Very usefully, the active material may be saturated in the solvent. The carbon nanotube film structure 16 can be advantageously immersed in the preform of the active material for a period of time until the solvent is completely volatilized. Thus, the particles of active material 28 can be dispersed uniformly in the carbon nanotube film structure 16.

In another embodiment of step (f), the preform can be, in a useful manner, the active material in a gaseous state at elevated temperature. The carbon nanotube film structure 16 may be disposed directly in the gas of the active material for 0.5 to 2 hours in a protective gas. After cooling to room temperature, the particles of active material 28 can be uniformly formed and dispersed in the carbon nanotube film structure 16. The protective gas can be beneficially prepared from at least nitrogen (N2), ammonia (NH3 ), and a noble gas.

In step (f), the precursor is a mixture of at least two reactants to prepare the active material. The reactants can be, in a timely manner, in the gaseous state, liquid state, or mixed with a solvent. The carbon nanotube film structure 16 may be suitably submerged in the precursor for a period of time. After the reaction of the reactants, the particles of active material 28 can be uniformly formed and dispersed in the carbon nanotube film structure 16. It is understood that the impurities formed by the reaction can be removed by a washing / filtration step .

In the present embodiment, the preform is a saturated solution of LiCoO2 in water. The carbon nanotube film structure 16 is immersed in the preform for several hours until the water is consumed. Thus, in the second carbon nanotube structure 24 that results, the LiCoO2 particles are uniformly dispersed in the carbon nanotube film structure 16.

In step (g), the positive current collector 22 may be beneficially a metal substrate. Very suitably, the metal substrate is a copper foil.

It is to be understood that, in step (g), the positive current collector 22 in the lithium battery cathode is optional. In another embodiment, the lithium battery cathode may include only the second carbon nanotube structure 24. Because a plurality of carbon nanotube films overlap to form a self-sustaining and stable film structure, the second structure of Carbon nanotubes 24 can only be used as the cathode of the lithium battery without the positive current collector 22.

The cathode 20 of the present embodiment includes the structure of carbon nanotube films 16 and the particles of active material 28 uniformly dispersed therein. As such, the conductivity of the cathode can be increased. In addition, the capacity of the lithium battery using the cathode 20 described above can be improved due to its reduced resistance. Additionally, the method for manufacturing the cathode 20 described above is simple and suitable for series production.

Referring to Figure 12, a lithium battery 100 includes a container 50, an anode 10, a cathode 20, an electrolyte 30, and a separator 40. The anode 10, the cathode 60, the electrolyte 30, and the separator 40 they are arranged in the container 50. The container 50 is filled with the electrolyte 30. The cathode 20 and the anode 10 are separated by the separator 40. The cathode 20 includes a positive current collector 22 and a second carbon nanotube structure 24 about him. The second carbon nanotube structure 24 includes a carbon nanotube film structure 16 and a plurality of particles of active material 28 dispersed in the carbon nanotube film structure 16. The anode 10 includes a negative current collector 12 and a first structure of carbon nanotubes 14 arranged on it. A positive terminal 80 is disposed on the upper parts of the positive current collector 22 of the cathode 20. A negative terminal 60 is disposed on the upper parts of the negative current collector 12 of the anode 10.

The materials of the cathode 30, the separator 40, and the electrolyte 30 may be common materials known in the art. In the present embodiment, the first carbon nanotube structure 14 is a film of carbon nanotubes with a plurality of carbon nanotubes aligned along a certain direction. The carbon nanotube film structure 16 includes at least two overlapping carbon nanotube films. The

particles of active material 28 may be prepared, in a timely manner, of transition metal oxides and mixed transition metal oxides such as lithium oxide and spinel manganese oxide (eg, LiMn2O4), lithium iron phosphate of olivine type (for example, LiFePO4), and stratified lithium and cobalt oxide (for example, LiCoO2). The weight of the anode is approximately 50 micrograms. The material of the separator is polyolefin.

Referring to Table 1, the performance in anode cycles based on carbon nanotubes of the lithium battery at room temperature is shown. The anode of the lithium battery has high charge / discharge efficiency, high capacity, and good cycle performance. The discharge capacity of the first cycle of the lithium battery is above 700 mAh / g. The efficiency of the first cycle is above 140%. After 11 cycles, the capacity retention is above 90%.

Table 1

Number of cycles

Charging current (mAh) Discharge current (mAh) Efficiency

one

0 0.1094  0

2

0.0255 0.0382 149.8

3

0.0270 0.0321 118.5

4

0.0252 0.0293 116.2

5

0.0242 0.0277 114.1

6

0.0241 0.0271 112.3

7

0.0236 0.0264 111.6

8

0.0234 0.026 110.8

9

0.023  0.0259  110.3

10

 0.0227 0.0257 109.1

eleven

 0.0229 0.0259 109.6

12

 0.0226 0.0254 108

13

 0.0227 0 0

It will be apparent to people with normal ability in the field of the present invention, that the composition of the cathode and the electrolyte is not limited to the materials mentioned above. The carbon nanotube film has essentially no binder, and includes a large number of micropores. The amount of intercalation of lithium ions can be increased, due to the special microporous structure of anode sheets. The stability of the SEI layer formed in the first loading and unloading cycle can be improved due to the carbon nanotube film. As such, the electrolyte used in the lithium battery can be selected from a wider range of common electrolytes. Additionally, carbon nanotubes are grown uniformly in the arrangement of carbon nanotubes. As such, the carbon nanotubes that have been grown are uniformly dispersed in the carbon nanotube film. The cathode 20 of the present embodiment includes the structure of carbon nanotube films 16 and the particles of active material 28 uniformly dispersed therein. As such, the conductivity of the cathode can be increased. In addition, the capacity of the lithium battery using the cathode 20 described above can be improved, due to its reduced resistance. Additionally, the method for manufacturing the cathode 20 and anode 10 described above is simple and suitable for series production.

It is also to be understood that the above description and claims oriented to a method may include some indication in reference to certain steps. However, the indication used should only be seen for identification purposes and not as a suggestion as to an order for the stages.

Claims (6)

1.-A lithium battery, which includes: an anode comprising a carbon nanotube film structure comprising at least two overlapping carbon nanotube films, in which each carbon nanotube film comprises a plurality of consecutive carbon nanotubes joined end to end and aligned along the same address; a cathode; a separator used to separate the anode from the cathode; a vessel with the anode, cathode and separator disposed therein; Y an electrolyte that fills the container. 2. The lithium battery according to claim 1, further comprising a negative current collector, and the carbon nanotube film structure is arranged on a surface of the current collector. 3.-A lithium battery, which includes: an anode; a cathode comprising a carbon nanotube film structure comprising at least two overlapping carbon nanotube films, and a plurality of particles of active material dispersed in the carbon nanotube film structure, in which each carbon nanotube film comprises a plurality of consecutive carbon nanotubes joined end to end, and aligned along the same direction; a separator used to separate the anode from the cathode; a vessel with the anode, cathode and separator disposed therein; Y an electrolyte that fills the container. 4. The lithium battery according to claim 3, wherein the diameter of the particles of active material It is in the approximate range from 3 nanometers to 10 nanometers, and the active material particles can be prepared from transition metal oxides and mixed transition metal oxides such as spinel-type lithium and manganese oxide, lithium iron phosphate and olivine type, and stratified lithium and cobalt oxide. 5. The lithium battery according to claim 3, further comprising a positive current collector, and the carbon nanotube film structure is arranged on a surface of the positive current collector. 6.-A method for manufacturing an anode of a lithium battery, the method comprising the steps of:

(to)

provide a disposition of carbon nanotubes;

(b)

preparing a carbon nanotube film structure comprising at least two overlapping carbon nanotube films, wherein each carbon nanotube film comprises a plurality of consecutive carbon nanotubes joined end to end and aligned along the same address;

(C)

provide a negative current collector; Y

(d)

arrange a carbon nanotube film structure on the current collector, and thereby obtain the lithium battery anode.

7. The method according to claim 6, wherein step (b) further comprises the following steps of: (b1 ”) extract at least two carbon nanotube films from the carbon nanotube arrangement, using a utensil; (b2 ”) provide a support member and arrange the at least two films of carbon nanotubes in the support member along different directions, the at least two films of carbon nanotubes overlapping each other to obtain the structure of Carbon nanotube films. 8. The method according to claim 7, wherein step (b1 ") further comprises the following steps of: (b1" 1) selecting a plurality of carbon nanotube segments with a predetermined width; (b1 "2) remove the carbon nanotube segments at a constant / uniform rate to form a film of carbon nanotubes; (b1 "3) repeat step (b1" 1) and (b1 "2) to form a plurality of carbon nanotube films. The method according to claim 7, wherein the structure of carbon nanotube films has a plurality of micropores, defined by the spaces between adjacent carbon nanotube segments. 10. The lithium battery according to claim 1, wherein the carbon nanotubes in the carbon nanotube film are joined end to end by the attractive force of Van der Waals.